1. Field of the Invention
The present invention relates to a thin-film magnetic head for applying to magnetic recording, especially to a tape head for reading data from a magnetic tape and writing data to the tape. The present invention further relates to a controlling method of a magnetic spacing that is a distance between the end of the magnetic head element and the surface of the recording layer of the magnetic recording medium.
2. Description of the Related Art
In recent years, magnetic recording and reproducing apparatuses have been remarkably improved in capacity of storage data due to the widespread use of multimedia and the Internet. And magnetic tape apparatuses for backing up or storing data are no exception of this trend of larger capacity, and have been required to be improved in a real recording density corresponding to the larger capacity.
Thin-film magnetic heads are widely used, in the above-described magnetic recording and reproducing apparatuses, for writing data to a magnetic recording medium and reading data from the medium. The thin-film magnetic heads have also been strongly required to be improved in performance corresponding to the larger capacity, especially to appropriately control a magnetic spacing in order to stably perform read and write operations under higher recording density and to maintain original lifetime of the thin-film magnetic head. Here, the magnetic spacing is defined as a distance between the end of the magnetic head element of the thin-film magnetic head and the surface of the recording layer of the magnetic recording medium.
One of the most effective method for controlling the magnetic spacing is to adjust the pressure working between the thin-film magnetic head and the magnetic recording medium. For example, in a magnetic disk apparatus, the thin-film magnetic head flies above the rotating magnetic disk, and thus receives a certain negative pressure (a pressure by which the head and the disk are attracted to each other) generated by laminar air flow between the head and the disk. The negative pressure is balanced with an adjusted pressure which the suspension supporting the head brings to the head, to maintain a predetermined magnetic spacing.
As a measure for positively controlling the magnetic spacing by adjusting the pressure working between the thin-film magnetic head and the magnetic recording medium, for example, Japanese Patent Publication No. 2003-272335A describes a technique in which the head end surface is protruded toward the magnetic disk by heat generated from a heater provided within the thin-film magnetic head for a magnetic disk apparatus. Further, Japanese Patent Publications Nos. 08-212740A and 09-198829A describe techniques for dissolving the adsorption between the head and the magnetic disk.
Also in the thin-film magnetic head for a magnetic tape apparatus (tape head), to adjust the pressure working between the tape head and magnetic tape is an extremely effective method for appropriately controlling the magnetic spacing. Here, the tape head and the magnetic tape as a magnetic recording medium are usually contacted with each other by receiving a certain suppress force which causes them to head toward each other. Therefore, it is important for controlling the magnetic spacing to adjust the suppress force. As an example of intending to adjust the suppress force, Japanese Patent Publication No. 2004-295951A discloses a technique of utilizing a negative-pressure slider.
However, there has been a problem that the magnetic spacing is likely to vary due to the change in pressure working between the thin-film magnetic head and the magnetic recording medium derived from the change in shape of the medium-opposed surface of the head, generated by the contact between the head and the medium.
Especially, the tape head slides on the magnetic tape during read and write operations. Therefore, the shape of the tape bearing surface (TBS), which is a medium-opposed surface as well as a sliding surface, varies over time due to the friction with the magnetic tape. The variation of the shape becomes more rapid when the suppress force working between the tape head and the magnetic tape is set to be larger. Further, the variation becomes more drastic in the case that the magnetic tape contains abrasive. As the case may be, the lifetime of the tape head would be reduced by excessively decreasing the magnetic spacing due to the wear of the head generated from the increase in the degree of contact between the head and the magnetic tape. Further, in some cases, the head performance may be degraded due to frictional heat generated by the contact. Furthermore, in some cases, the magnetic spacing may become larger due to the change in shape of the TBS, which would cause the read output to be decreased, or cause the peak steepness of the read signal to be degraded. Therefore, in the tape head, it is significantly important to control the magnetic spacing appropriately by stably adjusting the pressure working between the head and the magnetic recording medium according to the change of conditions such as the change over time. This adjustment of the pressure also becomes significantly important for other thin-film magnetic heads such as a thin-film magnetic head for magnetic disk.